From: Nutomic <me@nutomic.com>
Date: Thu, 6 Jul 2023 12:29:51 +0000 (+0200)
Subject: Only allow http(s) scheme for urls (ref #3505) (#3508)
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Only allow http(s) scheme for urls (ref #3505) (#3508)

With this change only http(s) schemes are allowed for post.url
field. This is checked for incoming api and federation requests.
Existing posts in database which are sent to clients are not
checked. Neither does it check urls in markdown.
---

diff --git a/crates/api_crud/src/post/create.rs b/crates/api_crud/src/post/create.rs
index 1dcc9024..13d896b4 100644
--- a/crates/api_crud/src/post/create.rs
+++ b/crates/api_crud/src/post/create.rs
@@ -31,7 +31,7 @@ use lemmy_utils::{
   error::LemmyError,
   utils::{
     slurs::{check_slurs, check_slurs_opt},
-    validation::{clean_url_params, is_valid_body_field, is_valid_post_title},
+    validation::{check_url_scheme, clean_url_params, is_valid_body_field, is_valid_post_title},
   },
 };
 use tracing::{warn, Instrument};
@@ -58,6 +58,7 @@ impl PerformCrud for CreatePost {
 
     is_valid_post_title(&data.name)?;
     is_valid_body_field(&data.body, true)?;
+    check_url_scheme(&data.url)?;
 
     check_community_ban(local_user_view.person.id, data.community_id, context.pool()).await?;
     check_community_deleted_or_removed(data.community_id, context.pool()).await?;
diff --git a/crates/api_crud/src/post/update.rs b/crates/api_crud/src/post/update.rs
index 632bc5ae..a8c5715b 100644
--- a/crates/api_crud/src/post/update.rs
+++ b/crates/api_crud/src/post/update.rs
@@ -20,7 +20,7 @@ use lemmy_utils::{
   error::LemmyError,
   utils::{
     slurs::check_slurs_opt,
-    validation::{clean_url_params, is_valid_body_field, is_valid_post_title},
+    validation::{check_url_scheme, clean_url_params, is_valid_body_field, is_valid_post_title},
   },
 };
 
@@ -50,6 +50,7 @@ impl PerformCrud for EditPost {
     }
 
     is_valid_body_field(&data.body, true)?;
+    check_url_scheme(&data.url)?;
 
     let post_id = data.post_id;
     let orig_post = Post::read(context.pool(), post_id).await?;
diff --git a/crates/apub/src/objects/post.rs b/crates/apub/src/objects/post.rs
index 8064c771..d73642be 100644
--- a/crates/apub/src/objects/post.rs
+++ b/crates/apub/src/objects/post.rs
@@ -44,6 +44,7 @@ use lemmy_utils::{
     markdown::markdown_to_html,
     slurs::{check_slurs_opt, remove_slurs},
     time::convert_datetime,
+    validation::check_url_scheme,
   },
 };
 use std::ops::Deref;
@@ -191,6 +192,7 @@ impl Object for ApubPost {
       } else {
         None
       };
+      check_url_scheme(&url)?;
 
       let local_site = LocalSite::read(context.pool()).await.ok();
       let allow_sensitive = local_site_opt_to_sensitive(&local_site);
diff --git a/crates/utils/src/utils/validation.rs b/crates/utils/src/utils/validation.rs
index e43ddbbb..b5ae5b74 100644
--- a/crates/utils/src/utils/validation.rs
+++ b/crates/utils/src/utils/validation.rs
@@ -302,12 +302,22 @@ pub fn check_site_visibility_valid(
   Ok(())
 }
 
+pub fn check_url_scheme(url: &Option<Url>) -> LemmyResult<()> {
+  if let Some(url) = url {
+    if url.scheme() != "http" && url.scheme() != "https" {
+      return Err(LemmyError::from_message("invalid_url_scheme"));
+    }
+  }
+  Ok(())
+}
+
 #[cfg(test)]
 mod tests {
   use super::build_totp_2fa;
   use crate::utils::validation::{
     build_and_check_regex,
     check_site_visibility_valid,
+    check_url_scheme,
     clean_url_params,
     generate_totp_2fa_secret,
     is_valid_actor_name,
@@ -519,4 +529,13 @@ mod tests {
     assert!(check_site_visibility_valid(false, false, &Some(true), &None).is_ok());
     assert!(check_site_visibility_valid(false, false, &None, &Some(true)).is_ok());
   }
+
+  #[test]
+  fn test_check_url_scheme() {
+    assert!(check_url_scheme(&None).is_ok());
+    assert!(check_url_scheme(&Some(Url::parse("http://example.com").unwrap())).is_ok());
+    assert!(check_url_scheme(&Some(Url::parse("https://example.com").unwrap())).is_ok());
+    assert!(check_url_scheme(&Some(Url::parse("ftp://example.com").unwrap())).is_err());
+    assert!(check_url_scheme(&Some(Url::parse("javascript:void").unwrap())).is_err());
+  }
 }